Stool Culture
      
CPT
  87045; 87046; 87427
Synonyms
  Culture, Stool, Comprehensive; Enteric Pathogens Culture, Routine; Feces Culture, Routine; Routine Culture, Stool
Test Includes
  Culture; isolation and identification (at an additional charge) of Salmonella, Shigella, Campylobacter, and E. coli O157. If culture results warrant, susceptibility testing (additional charges/CPT code[s] may apply) may be performed. CPT coding for microbiology and virology procedures often cannot be determined before the culture is performed.
Special Instructions
  Specify specific pathogen if not Salmonella, Shigella, Campylobacter, or enterohemorrhagic E. coli (EHEC). Check expiration date of transport; do not use expired devices.

Fecal specimens for different tests often need different transport containers and different transport conditions (eg, frozen, raw stool). Specimens should be portioned out to separate devices of each type for each test requested before sending to the laboratory. Stool for bacterial culture and enterohemorrhagic E. coli Shiga toxin by EIA should be submitted in the C&S transport vial. Only a thumbnail size portion of stool, about 1 g or 1 mL, should be added to the vial. Overfilling the vial will reduce recovery of stool pathogens.

Specimens from sources, such as genital, stool, urine, upper and lower respiratory specimens, cannot be cultured under the aerobic bacterial culture test number. If specimens are incorrectly submitted with an order for aerobic bacterial culture, the laboratory will process the specimen for the test based on the source listed on the request form. The client will not be telephoned to approve this change, but the change will be indicated on the report.

Specimen
  Stool or rectal swab placed in stool culture transport vial
Volume
  1 g, 1 mL, or one swab in stool C&S transport vial (the usual bacterial swab transport is not acceptable although the swab may be used).
Container
  Fecal transport system is required. Diapers are not acceptable. Culture collection swab may be used to collect rectal swabs or a swab of fecal material, then swab should be placed in C&S vial (fecal transport system).
Collection
  A single stool specimen cannot be used to rule out bacteria as a cause of diarrhea. More than two specimens should only be submitted from patients for whom there is a high degree of suspicion. Hospitalized patients who develop diarrhea while hospitalized and more than 72 hours after admission should be tested for Clostridium difficile by detection of either Toxin A or Toxin B testing or both.

Studies have shown that patients who did not have gastroenteritis or other GI symptoms on admission are unlikely to have diarrheal illness due to Salmonella, Shigella, Campylobacter, or enterohemorrhagic E. coli.

Stool: Specimen should be collected in sterile bedpan, not contaminated with urine, residual soap, or disinfectants. Those portions of stool which contain pus, blood, or mucous should be transferred to sterile specimen container.

Rectal swab: Pass swab beyond anal sphincter, carefully rotate, and withdraw. Swabbing of lesions of rectal wall or sigmoid colon during proctoscopy or sigmoidoscopy is preferred.

Duodenal or sigmoid aspirate: Specimen should be collected by a physician trained in this procedure.

Stool specimen can be divided for other types of cultures by laboratory. Miscellaneous tests and ova and parasites tests should be split into appropriate containers and transport prior to shipping to laboratory.

Storage Instructions
  Maintain specimen at room temperature.
Causes for Rejection
  Specimens received in grossly leaking transport containers; diapers; dry specimens; specimens submitted in fixative or additives; specimens received in expired transport media or incorrect transport device; inappropriate specimen transport conditions (not in a C&S vial or in an overfilled C&S vial); specimens received after prolonged delay in transport (usually more than 72 hours); specimens stored or transported frozen; wooden shaft swab in transport device; unlabeled specimen or name discrepancy between the specimen label and the request form
Use
  Detect bacterial pathogenic organisms in the stool; diagnose typhoid fever, enteric fever, bacillary dysentery, Salmonella infection.

Indications for stool culture include:1

  • bloody diarrhea
  • fever
  • tenesmus
  • severe or persistent symptoms
  • recent travel to a third world country
  • known exposure to a bacterial agent
  • presence of fecal leukocytes
Limitations
  Yersinia sp and Vibrio parahaemolyticus will not be isolated unless specifically requested; these will each be done with an additional charge. These organisms are fastidious and have very specific requirements for growth.
Methodology
  Aerobic culture on selective media; detection of EHEC Shiga-like toxins by enzyme immunoassay.
Contraindications
  A rectal swab culture is not as effective as a stool culture for detection of the carrier state.
Additional Information
  In enteric fever caused by Salmonella typhi, S. choleraesuis, or S. enteritidis, blood culture may be positive before stool cultures, and blood cultures are indicated early; urine cultures may also be helpful.

Diarrhea is common in patients with the acquired immunodeficiency syndrome (AIDS). It is frequently caused by the classic bacterial pathogens as well as unusual opportunistic bacterial pathogens and parasitic infestation. (Giardia, Cryptosporidium, and Entamoeba histolytica frequently reported.) Cryptosporidium and Pneumocystis can occur with AIDS. Rectal swabs are useful for the diagnosis of Neisseria gonorrhoeae and Chlamydia infections. AIDS patients are also subject to cytomegalovirus, Salmonella, Campylobacter, Shigella, C. difficile, herpes, and Treponema pallidum gastrointestinal tract involvement.
 

Diarrhea Syndromes Classified by Predominant Features

 
Syndrome
(anatomic site) 
Features  Characteristic Etiologies 
Gastroenteritis (stomach)  Vomiting  Rotavirus 
    Norwalk virus 
    Staphylococcal food poisoning 
    Bacillus cereus food poisoning 
Enteritis
(small bowel) 
Watery diarrhea
Large-volume stools, few in number 
Enterotoxigenic Escherichia coli 
    Vibrio cholerae 
    Any enteric microbe 
    Inflammatory bowel disease 
Dysentery, colitis (colon)  Small-volume stools containing blood and/or mucus and many leukocytes  Shigella 
    Campylobacter 
    Salmonella 
    Invasive E. coli 
    Plesiomonas shigelloides 
    Aeromonas hydrophila 
    Vibrio parahaemolyticus 
    Clostridium difficile 
    Entamoeba histolytica 
    Inflammatory bowel disease 

In acute or subacute diarrhea, three common syndromes are recognized: gastroenteritis, enteritis, and colitis (dysenteric syndrome). With colitis, patients have fecal urgency and tenesmus. Stool are frequently small in volume and contain blood, mucus, and leukocytes. External hemorrhoids are common and painful. Diarrhea of small bowel origin is indicated by the passage of few large volume stools. This is due to accumulation of fluid in the large bowel before passage. Leukocytes indicate colonic inflammation rather than a specific pathogen. Bacterial diarrhea may be present in the absence of fecal leukocytes and fecal leukocytes may be present in the absence of bacterial or parasitic agents (ie, idiopathic inflammatory bowel disease).2 See table. Although most bacterial diarrhea is transient (1-30 days) cases of persistent symptoms (10 months) have been reported. The etiologic agent in the reported case was Shigella flexneri diagnosed by culture of rectal swab.3 In infants younger than 1 year of age, a history of blood in the stool, more than 10 stools in 24 hours, and temperature greater than 39C have a high probability of having bacterial diarrhea.4,5 Diarrhea is also a common side effect of long term antibiotic treatment. Although often associated with Clostridium difficile, other bacteria and yeasts have been implicated.